FAQ: Cheaply Keeping a Pool Hot -- 90F,95F,100F -- How we ran till Jan 11th in Canada

[Uavmx]

Hopefully mdr/Mark will pop in with his experience on the run up - as my methods are not presently in open air, though I did run open through very low temps before installing the dome.

How many BTU is your heater? If your temps are above freezing, which they sound like they are, I'd run the heater on max until you get to your desired temp...with pump on full if your heater needs the pressure to operate (low flow causes problems in heaters). The key is to NOT thermostat on the run up...run full to max.

While night means the ambient air is colder, and your temp gain might be a bit slower, I've not noticed a huge differential -- here where its below freezing, I actually run the heater only at night to gain back the 5-6 degrees I might lose during the day. In my case, I run at night because I want it to therapy temp for the am (95 degrees) but can still comfortably swim during the day without the heater on as I only lose 1/3 to 40% of a degree an hour depending on how far below freezing I am. As a result, my heating time and ergo cost can be as low as 5 hours up to the most I've needed in bitter cold of around 10 hours.

Once you're at desired temp, leaving the water covered and still until use seems to preserve heat the best. But in my case I keep the pump running to operate my air blower warmer that uses the pool water...and to avoid any pipe problems in an area exposed that comes out from the pool house. In your shoes if I had the option, my daytime, non-heating hours would be run on low speed. But i only have a single speed pump.

Best wishes for an awesome swim holiday

Thanks, kind of what I assumed. Btu is 250k.


Sent from my iPhone using Tapatalk

 

[mdrejhon]

First question: When doing the initial 24-48 hour increase (I think need to move it from 50-95) is it best to run it 24 hours into the cold night? Or shut it down at night and only run it during the daytime hours. Let's assume I have plenty of time (4-5 days) to heat up the pool if I want to.

Secondly: Do you run your pump at full speed? I have a VSP, currently it needs to be running full to get the heater to see the pressure (but I think I can fix it if needed) is there value in trying to run it a little slower?

1. Full speed pump when heating. Better heating efficiency.
2. Continuous run overnight (make sure heater has BOTH overpressure/overtemp safeties).
3. Heater set to maximum temperature (or slightly above target temp)
4. Pool always covered up. Only uncover whenever swimming.
5. Pump OFF or pump trickle speed (drip,drip) whenever not heating.

On that note, we are going yearround with no pool closing, and thanks to the new heater/new pump, we have discovered a new way of doing things:

The pump can control the heater
And definitely turn off pump or use super slow trickle pump speed (e.g. 25 watt, ~700rpm) as pipe-freeze protection when not heating. Heaters will often automatically turn off when the pump speed is slow, so with modern heaters (with BOTH a pressure switch AND an overtemperature switch) can safely be controlled by the pump speed. And apparently, some pumps have built-in programmable timers. Which solves quite a few problems without yet desparately needing a central automation system yet...

Some pool pumps have a trickle speed mode, which is good for preventing frozen pipes
These are the sub-1000rpm modes in some variable speed pumps like Hayward TriStar VS. I found out my Hayward Tristar VS pump can throttle all the way down to less than 1 cubic inches per second per jet nozzle (3 nozzles), which is amazingly slow. Almost equal to not running at all. The pool pump goes all the way down from 1000-1500 watts (at 3250rpm+) to less than 30 watts at trickle pump speed (700rpm). There's a nonlinear relationship between water flow and the pump rpm, so pool pump power consumption is less than a lightbulb during trickle mode!! Which is quite convenient because the pool heater automatically turns off when the pump runs slow.

I also installed a rudimentary ground thermometer as redundancy (cheap 20 inch soil themometer, analog dial on top of a 20 inch metal pole, purchased off eBay for 25 bucks). This allows me to determine how much risk the pipes are in freezing, so I can completely turn off the pump at other times. Ground is 39-40F so far, even on the coldest days; the ground temperature isn't budging at all.

Pool Pump Timers are VERY helpful!
Since my new pool pump has a timer, I've programmed the pump timer to run max speed (3250rpm) for 4 hours from 12am-4am which automatically turns on the heater (pressure flow switch), and then min speed for 20 hours (700rpm) as pipe freeze protection.

Determining how long I need to run pump to heat pool target 95F temperature
Whenever I need to heat up before a weekend,
1. I briefly run the pool heater for 15-30 minutes (override the pool pump timer) to stir up the pool properly. Very important to do a pool stir, as temperature difference between top and bottom of pool can become signifcant.
2. I check the skimmer dip thermometer for current water temperature (more accurate than temperature meter on heater)
3. The difference between current and destination temperature is the number of hours I need to run heater at (250KBtu on a covered-up 20,000 gallon tends to takes approx 1 hour per 1 degree when above 70F). For 75F to 95F jump, I start the heater about 20-24 hours in advance.

Briefly overriding the pump's timer mode
The speed buttons on a Hayward Tristar VS behaves as timer overrides -- and lasts for up to 12 hours. I've reprogrammed Speed 1 to become 700rpm 12hour, and Speed 4 to become 3250rpm 12hour (on one press), as my convenient heating button / pipe-freeze trickle button.

With the Hayward Tristar VS, I do have to push the "Speed 4" button once every less-than-12-hours to keep the pump speed high (to override the timer). When I leave pump attended for more than 12 hours, the pump automatically goes back into its timer program. Which means it's safe for me to ignore the pump for days, the pump automatically goes back to its timer program (4hour-20hour heat-vs-trickle cycle) which is perfect for mid-winter weekend getaways without worrying about my pool.

I've reprogrammed the "Speed 1" button on the Hayward TriStar VS to a 700rpm speed, since that's the minimum reliable speed that the water trickles through the pipes. If I want to turn off the heater but avoid worrying about frozen pipes, I just press "Speed 1" button on the Hayward Tristar VS pump (heater automatically turns off). If I want to heat the pool, I just press "Speed 4" on the pump and the heater automatically turns on.

Going on vacation, with unattended timered heating operation
I went on vacation and let my pool operate the heater unattended using the 4hour-20hour timer programmed into the Hayward Tristar VS pump. 4 hour max speed pumping heated (12am-4am), and 20 hour almost-turned-off trickle speed pump (4am-12am) trickling the water at mere 1 cubic inch/second per jet nozzle to preven frozen pipes while avoiding cooling down the pool noticeably. I left on December 24th with the pool temperature at 95F. I returned on December 31st with the pool temperature at 79F, so I only needed to run about 16 hours of heating to boost it right back up. It was below freezing most of these days (albiet slightly above sometimes during the days).

WARNING ABOUT UNATTENDED HEATING OPERATIONS DURING VACATION
Recommended only for modern new heaters & new pumps only. Please get your system fully checked by a licensed professional before attempting. Verify fully tested water pressure switch (confirmed) and fully tested overtemperature switch (confirmed) in case of water pressure switch failure. Use a puck chlorinator, set to a setting of around ~1 of 1-9 to maintain chlorine level (4hr timered fast pump/day) or setting 0.5 (8hr+ timered fast pump/day). Use a pump timer (or automation system) to control the heater. Use pump trickle mode (ultraslow drip flow) to prevent pipe freeze. (For a Hayward TriStar VS, that's 600-800rpm) Use a thermostatted safe electric heater for your pool shed housing the heating/pump equipment, set it to somewhere slightly above freezing, like 5C. Install GFCI protection in case of poolhouse flooding. Remote monitoring recommended (e.g. Power failure sensor, remote video camera, etc) so you can check poolhouse is in fine shape, though I haven't installed that latter part yet -- but soon.

Central smarthome automation system is not critical if you can use pool pump timers
I will have a more elaborate automation system but the Hayward pool pump timer system is a creative way to let my pool maintain itself for a week or two midwinter while I'm on vacation. I also have a 400 watt room convection heater panel for the poolshed building, to prevent the poolhouse from freezing. It thermostats off when the room warms up (when the pool heater runs) and thermostats back on if the interior of poolhouse gets close to freezing, preventing the indoors from being below freezing. The system is simple, heater is always turned on and I let the pool pump control the heater (heater turns off automatically when the water flow is slow). There is also overtemperature protection built into Raypak in case the water pressure switch ever fails, so I've got a backup and can trust the system to run attended.

We are now officially beginning yearround operation
After trialing the system so far, we have decided to run the pool through the winter without closing it down.

We're going domeless:
Foam cover upgrade & foam behind vinyl will be our future upgrades
We are now leaning towards skipping getting a pool dome since we're in an old urban neighborhood with small backyards (noise from a pool dome inflator will be an issue to five nearby properties). So instead purchasing a high-end foam roller cover (1/4 or 1/3" foam) and then installing foam when re-vinyl-linering. Full foam covers are extremely expensive and roll up to a really thick roll. But that'll thermos-bottle the pool, top, bottom, and all sides, whenever it is not in use. We'll need to double-cover the pool (foam cover floating on the water, then some kind of a quick-remove winter cover hovering above, to keep debris out and make debris sweeping easy) since we probably intend to probably do domeless 12-month operations.

 

[mdrejhon]

New tip:
Decorative laser projectors are wicked cool with steam rising from a hot tub -- especially a pool sized one.

The lasers, normally not visible in air, becomes very visible in the steam. You can buy these laser projectors for about $20-$30 at many places (the cheaper "AS SEEN ON TV" units), though we got some higher end NOMA's with blue lasers too (Canadian Tire, reg $219.99 CAD, boxing day sale $54.99 CAD, or less than $40 USD!). We now have 3 laser projectors, 2 of them currently in use on hottubbed pool nights. I prefer the NOMA units (or good brands) because they operate properly down to -30C, as the cheap laser projectors started going dim/dark on freezing nights.

In the photo, the laser projector unit is sitting 10 feet away on top of the porch, but looks much closer because of the solidness of the laser beams going through the steam. Quite a dramatic effect.

The laser can be set to change color from red/green/blue or alternate.

The battery powered waterproof christmas lights (PLAYBULB Light + PLAYBULB Extension) are Bluetooth controllable from a smartphone, to be set to any one of 16 million colors or a rotating colors, or candlelight flicker.

All lighting in the photo costs less than $50 USD for each ($100 total)....not bad for fancy pool lighting far superior to poolshop stuff!

 

[Swampwoman]

Cool lights and neat info re VS pump

Just so you know, dome blower is pretty quiet. Eg. Absolutely can't hear inside house and mine is about 30' away from master BR window. Our home runs on boiler, so quiet in winter with no canceling noise. With that said, nothing like the open sky for periodic use

 

[mdrejhon]

Either way, thanks for the info on the dome blower! It may not sway community concern and the pros of open sky may outweigh, as long as the pool can get double-covered when not in use somehow.

 

[Swampwoman]

Yes, for casual use, I love open sky, so if I weren't trying to keep mine to 95 degrees daily for physio, the dome wouldn't be as much of a boon. But for physio and weather-free swimming, it rocks! I get my night sky hit from the (separate) hot tub

 

[duraleigh]

I have only skimmed this thread. How many hours weekly do you spend managing your pool?

 

[mdrejhon]

I have only skimmed this thread. How many hours weekly do you spend managing your pool?

It varies a lot. A few hours a week.

Long answer:

In our photos, you can see that there is a fair bit of foilage surrounding our pool. It consists of 1/4 to 1/2 of our pool maintenance overhead (debris that needs to be saept off cover, vaccuumed from bottom, and skimmed with net from top), depending on season, amount of wind, and also fall season.

Worst case scenario, if we are swimming everyday, AND during windy weather, about an hour a day because of the tree debris falling onto the pool cover, as we always cover when unused. Some days are less windy than others. We use a sweeper on a pool pole to clean our cover before unrolling.

Better case, in calm weeks, and if I unroll cover only halfway (no need to sweep every single time), only a few minutes a day.

Until debris becomes visible at the bottom of the deep end and black dust (dead algae, etc) appears, then I have to vaccuum, usually twice a week, but I try to cover-sweep first carefully if its an easy sweep/dry cover once a week. Then I only need to do the full-pool vaccuum once a week (goal not always achieved).

If we are swimming just weekends, no work done during week (except quick tests, and very occasional liquid chlorine and sometimes Ph+/Ph-) then 1.5 hour work on the Friday (or Thursday) to deal with tree debris buildup sitting on top of pool and the weekly vaccuuming since tree debris "seeps into the cracks" at the edges of the cover.

For wet pool covers fermenting for many days with leaf/needle debris, careful sweeping cover takes longer than a vaccuuming (ugh!) as I then have to scoop dirty water using cups as I unroll the pool cover a half meter (one or two feet at a time) since I don't want that brackish tree-debris stewed water on top of cover to flow into pool). +30min extra if it was a windy rainy storm on Thursdays.

I quickly test at least free chlorine and Ph everyday as a warmer pool can eat chlorine fast. Then after a vaccuum, pool is sparking and ready all weekend, as its usually a quick light easy cover sweep of minor dry debris on consecutive swim days.

Average? Totalled? Probably 3 hours a week.
Including the quick skimming moments with with the net.

 

[mdrejhon]

I was just thinking about you yesterday during our snowstorm
We've gotten more than 8" but given pace of it, the dome did not go down. I lost 4 degrees in 12 hours with the heater off, so recovered it pretty easily

I'm doing some thermodynamical calculations since I am naturally curious.

So in a snowstorm you lose 4F in 12 hours. What was the air temperature at the time? Was it with dome only, or with both dome, and pool cover?

Note about measuring temp:
- Dip thermometer is more direct measurement than digital thermometer built into pumps/heaters which can read cold/hot.
- At max pumping speed with heater, after running for an hour, my Raypak Digital thermometer reads 5F higher than a dipped thermometer in the pool. It can vary from 2F to 8F higher depending on variables like pump speed and how long the heater has been running. So I rely on dip thermometer
- When measuring temp, I always first turn on (or throttle up from trickle speed) the pump to stir the pool first before reading the dip thermometer (and snce it's being turned on, heater also kicks on too) at max speed for 15 minutes, to stir the pool. There is thermal gradients in stationary water, so I need to stir it up when I want to measure an accurate reading.

That's darn nearly the same rate of coolingn as mine (at least from 95F). I lost 5F in 10 hours but the temps were unusually chilly alst night (air temp low of -14C, about 7F). The inflatable pool dome will not affect your ground temperatures, so I think this is just about right for non-foam-lined vinyl covered pool, right?

To save heating a bit mid-week between heated weekends, I let my pool cool down to as low as ~70F. (Some weeks I don't let it go below 75F or 80F, depending on when I think I will next swim). It loses heat much faster at 95F than at 70F. So if I am maintaining for 5 days it's best to do a series of mini-boosts daily (a few hours a day) leading up to a big Thursday/Friday boost (less total heating hours) than continuously trying to maintain 95F. I try to approximate this by using a min/max speed timer on the Hayward Tristar VS, while also selectively overriding using the Speed1/Speed4 buttons once every couple days.

Swampwoman, you've been using my heater tricks -- can you tell me how much you think I'm saving you in your natgas bill -- with the pump-off-and-covered tricks?

 

[Swampwoman]

I monitor my actual pool temp with an "ambient weather" brand in-water sealed temp sensor that relays info to my setup, whch reads/reports 3 additional sensors...one in pool, one in dome, one inside air blower heater casing and one inside insulated box where pipes leave the pool house.

I haven't turned off the pump off at all since seriously freezing temps started several weeks ago...we decided it wasn't worth the risk So my experience is not at all a fair representation of what's possible. My goal has been to keep my operating cost/gas use under approx $15/day (eg about 21-22 CCF gas) (and keep water above 90 degrees at all times for daily heat up speed.) The max the heater could use in a day based on its btu ratings efficiency is around $33.

BUT In our case, we are constantly chilling the water two ways...first, by running through cold ground, then secondly, by running through the air heater that fits over the air blower just outside the dome, which warms the dome air by xtracting heat from the cycling water and returning much cooler water via hose back into the pool. (I'm running it via a shutoff valve I tricked out on a return to avoid ALL the heated water from going through.)

With that said, our rate of heat loss goes something like this...if in teens to 20s, roughly a third of a degree an hour; in the zero to 10 degree range we might lose closer to .4 or even .5 degrees an hour, especially if daytime temps are low next day.

In all cases, we leave the pool covered with a 12 mil clear cover except for an hour r two each day, which right now seeme to heat up ar by 10+ degrees. And to date, the dome has remained inflated. The air temp side the dome ranges from 40 degrees (39 lowest to date) after sitting idle and unheated to about 65 degrees.

The amazing part to me is that when in the very low-near-zero range, just turning the heater back on to net a partial degree can move the air temp by several degrees very quickly.

 

[mdrejhon]

I monitor my actual pool temp with an "ambient weather" brand in-water sealed temp sensor that relays info to my setup, whch reads/reports 3 additional sensors...one in pool, one in dome, one inside air blower heater casing and one inside insulated box where pipes leave the pool house.

I plan to get a temperature logger to monitor heating rates and cooldown rates.
(...Wouldn't it be fantastic if I can export it to Excel and see graphs of heat-up and cool-down curves...)

I haven't turned off the pump off at all since seriously freezing temps started several weeks ago...we decided it wasn't worth the risk So my experience is not at all a fair representation of what's possible. My goal has been to keep my operating cost/gas use under approx $15/day (eg about 21-22 CCF gas) (and keep water above 90 degrees at all times for daily heat up speed.) The max the heater could use in a day based on its btu ratings efficiency is around $33.

You said you have a 2 speed pump, rather than a variable-rate pump? I presume you use the low speed when not heating, and high speed when heating? It will not conserve as much as trickle speed (on a good variable speed) or turned off, but I am interested if you measured the difference of your cooldown rate between full speed and lower speed.

With that said, our rate of heat loss goes something like this...if in teens to 20s, roughly a third of a degree an hour; in the zero to 10 degree range we might lose closer to .4 or even .5 degrees an hour, especially if daytime temps are low next day.

This is roughly consistent with my experience. Non-foam-lined vinyl covered pool too, right?

You are a cost of .70 per CCF? After converting cubic meters to CCF and including my taxes, I am approx .55-.60 CCF. We have been running more often in colder weather than last year, but still cooling down a little midweek to m0inimize heater running time.

--EDIT--
Picture of current pump timer program. Now that I have to go through multiday always-below-freezing, I now more appreciate the pool pump timers a lot more. It's going to delay my need for an automation system a while longer.

-- trickle speed 20 hours

-- heating 4 hours (heater automatically turns on at >1500rpm)

-- wattage at slowest trickle (~1 cubic inch/second per jet nozzle)

At the moment over a 24 hour time period, pool heats up by approximately 4F (over 4 hours) and cools down by approximately 8-10F (over 20 hours) depending on what the pool temp is. This results in average 6F cooldown per day if pool already hot, and 4F cooldown per day if pool is already cool. So Sun-Mon-Tue-Wed-Thu looks approximately like 95F-89F-84F-78F-74F. The goal is to keep it above 70F so reheats aren't too expensive, as we usually use heated pool only weekends. Then one 20-24 hour Thurs-nite-to-Friday-evening overnight heating boost to bump it back up to 95F for the weekend (usually evening swims).

The night before we know we have a heated evening swim, we temporarily override/interrupt the timer by pressing the SPEED4 button (12 hours of 3200 RPM -- or was it 3250?). Unattended (without further button presses within 12 hours) the pool pump will automatically go back to the memorized timer.

It's not the ideal/perfect formula, but simpler, less manual, avoids frozen pipe worry, reduces work, and pool gets filtered everyday (without unnecessary cooling down of water) -- I am only using the pump's timer feature only.

Still saves lots of electricity & gas when not using pool midweek, and stays away from expensive Time-Of-Use electricity rates. We set-and-forget the heater (max temp) and never touch the heater, and only control the heater via the Hayward pump timers (relying on Raypak's own pressure switch to turn on heater).

 

[Swampwoman]

Re pump speed, I'm unfortunately one-speed so its full throttle until I get around to swapping in a 2 speed or variable speed

For the temp monitoring, I have the smaller unit sold with the pool float. In retrospect, I should have gotten the Ambient Weather station, which does log to pc software. Don't know if it works with Mac and I don't own any windows products, but if it does, that might be an upgrade for next year

For automation, I'd gotten an inexpensive PE653 Intermatic with remote. I just override the schedule as needed. Your solution is a nice benefit to your vs pump. For simple cheap automation, the pe653 is doing what I want in that I had the aquarite swg wired to its own port for independent scheduling because obviously I did not want it chained to the pump, which is running continually

Your nat gas rates are great. At Xmas I heard a lot from my Canadian sibs about hydro rates going through the roof so its good that at least NG is lower

To me, btw, the hydro rates don't seem that bad compared to my constant 14.7 kwh here in MI...especially when your off peak is 8 cents...but I guess that 18 cents peak hike was a shock to their system. I told them I'd trade free healthcare for the hydro rates any day (Yes, I know its not free and you pay it in taxes...I'm an expat...but its what I say when they feel too sorry for themselves to get a rise out of them )

 

[aussieta]

just wanted to add
we have solar heating and keep our pool around 80f in summer
just happened to be standing where the filter returns come back into pool
the water returning would have to be 10 degrees colder
so i was thinking the underground pipes need to be insulated
especially in your case

 

[Swampwoman]

We both would likely use less energy if they were, but conductive heat loss typically only accounts for about 10% of overall heatloss. The lionshare of heatloss from the pool is evaporation (70%) and radiant loss (20%). Which makes, in order or insulating priority, the cover the single most important, the walls a distant second, and the pipes third (unless exposed in part above ground, which mine are for about 2' coming out of my slab-built polebarn/poolhouse. That section I HAVE insulated heavily with Thermax and a wood box.)

So, lets say conductively speaking it takes 8 hours to turn over ALL 24,000 gallons of my water...without using the heater for those 8 hrs, I theoretically should "lose" about 9.5 degrees...but I don't lose anywhere near that inside that kind of time frame...due, I suspect, to closed system, motion and over time, (eg days) the warming impact of those same heated 24k gallons on the ground surrounding the pipes. So there's a time or flow impact in there somewhere.

Btw, Mark, you'd asked and I forgot to mention...no, our walls are not insulated beyond the typical foam used with composite walls but I'd expect the composite walls to be less conductive than say steel

 

[mdrejhon]

That said, when covered, that eliminates most of the "70%"
(percentages vary on variables and setup, but let's use the, for simplicity)

When covered is solved, the "20%" radiant loss and "10%" pipe loss.... becomes the major remaining factors. Relatively speaking, 20%:10% ratio means two-thirds radiant and one-third pipe loss (after you eliminate the 70%)

So if your pipes are not insulated, that is exactly why it is very worthwhile to turn off the pump (or dramatically slow it down) when not heating. Throttling pump when not heating saves me at least 100 a month in natgas. Nobody (except maybe ski chalet hot tubs and Norwegian spas) runs uncovered/undomed in winter 24/7 to 95F except during swims. Otherwise it can easily cost well north of 1000+ a month sustaining an open air hot pool. I'd have to run 24/7 all month long just to struggle to stay above 90F in winter, if I didn't cover it up.

But once covering is studious, that "70%" loss disappears. So non-insulated pipe loss mitigation measures like turning off/going trickle speed, has a noticeable jump -- such as a 400 bill down to 300 -- or some similar magnitude thereof, depending on your rates. Still a big jump. So that "10%" number (varies from setup to setup) is deceptively small -- still a big savings in the whole picture that could possibly easily pay off a VS pump within two years, by pipe heat loss savings alone.

I will this winter test full speed unheated versus trickle, and see how big my heat loss is, for some more definitive (less napkin) math...

Scientifically the exact percentages vary, but when heating bills are no longer 1000-1500 a month but closer to 200-300-400-500-600 including house heat (depending on your rates/weather), even a 100+ savings is mammoth, even with uninsulated in-ground pipes.

Even simple tricks become valuable where combined (pump turned off/trickle and others), you can get another 50%-70% savings (other tricks in this thread, turn off/trickle the pump, weekend-only operations, etc) compounded on top of a 70% savings (always covering when not in use). Which means it's possible to add 8 heated swim evenings per winter month (in 4 consecutive weekend blocs) for approximately one-order-of-magnitude lower natgas usage than an uncovered 24/7 always-heated pool.

just wanted to add
we have solar heating and keep our pool around 80f in summer
just happened to be standing where the filter returns come back into pool
the water returning would have to be 10 degrees colder
so i was thinking the underground pipes need to be insulated
especially in your case

My pipes are not insulated but they are in-ground and the equipment is inside an old detached brick garage turned into a poolhouse. Since my water is really truly flowing fast through pipes only a few hours a day, it is even smaller of a cost/inefficiency factor in my heated pool.

That said, Australia natgas rates are massively higher, and insulation is far more important. I notice your country has a manufacturer for thick foam roller covers which are not even made in Canada, I wish I had that! For next season (2017-2018) we are probably going to have to import a 1/4" foam pool cover, probably from the states.

 

[mdrejhon]

I measured my pool just before leaving work (I haven't touched the covered pool since Sunday night after .... whole system is on autopilot using the pump timer, 4h:20h heat:trickle cycle, and it was rechlorinated to 5ppm).

Current temp of pool is 79F as of Friday morning. I did not override last night (force heater always on) so it's on the usual timer program.

Sunday at approx midnight -- 95F (Might have been monday wee hours).
Friday at 8:00am -- 79F
-- I forced trickle mode at the conclusion of my Sunday swim (Mon wee hours), so it skipped the 12am-4am heat cycle for Mon wee hours.
-- So only 4 timered heater events occured, 4 hours each (Tue-Wed-Thu-Fri wee hours).
-- 16 hours of heater runtime
-- 104 hour time difference between 95F and 79F measurement.
-- Pool rechlorinated back to 5ppm after Sunday swim
-- Pool equipment completely untouched for 104 hours (always covered for the entire 104 hours, no buttons touched on any gadget/heater/pump) except water test to verify it's non-zero ppm.

Autopiloting-by-Hayward-builtin-timer: It ran the heater a grand total of 16 hours between the two (Tue-Wed-Thu-Fri wee hours timered heatups), and the temperature difference is only 16F as a result. This morning (Friday 8am EST) I just turned on the heater, so it'll reheat to a late-Friday-night swim (Extrapolating 11pm is probably going to be approx 92F, swimmable). I expect to run the heater approximately 24-28 hours this weekend grand total, to do the 95F evenings for Sat/Sun. (Approximately 8 to 10 hours beginning at noon-afternoon and turning off right after the evening swim, rinse and repeat 3 times a weekend, grand total 24 hours -- usually no swimming during daytime, just evening swims only) Note that the pump timers remains overriden all weekend long, because I prefer it run an approx 8h to 10h heating cycle beginning noon or early afternoon, and then jump into the pool towards the end of the heating cycle, enjoy the swim, then trickle the pump till tomorrow's reheat-up cycle for the next evening's swim.

There is now a lot of debris on the pool cover, so it'll be a big Friday night sweeping & vaccuuming for me. But at least I didn't do any pool work (except quick tests) since Sunday!

So approximately 40 hours of heater runtime per week to do 12 evenings of 95F wintertime swim weekends (16 hours timered during week, and the rest during weekend). That's 160 hours a month of Raypak runtime if current weather continues. 1 cubic feet of gas is roughly 1000 BTUs, so for 266K BTU/hr, that'll be 266cu/ft * 40hours = 10,640 cubic feet of gas per week = 106 CCF = approx $55/week (at my rates including taxes) for 12 Fri-Sat-Sun evenings of roughly 2-3-hour 95F swims. Concrete-vinyl pool without foam, simple bubble cover, sheltered pump/heater, and underground pipes [common setup]. Not bad, not bad!

SwampWoman, that would represent $70/week of pool-specific natgas for you at your rates, right? This is only rough napkin math, unscientific, but it really shows that this is really doable without too much bother with some simple digital Hayward pump timers (much simpler) that any everyday Joe user can do. I might be able to save maybe 4-8 hours with some advanced very-manual optimizations, but I'm not sure I want to bother (yet). The Hayward-built-in pump timer is a big time savings alone in the heat:trickle cycle.

This billing cycle because of vacation & because colder weather periods (there's several -15C moments) AND doing 12 swim evenings a month instead of 8 -- I'm expecting bill to rise to $350-$400 instead of being sub-$200. But if that's $220 for pool heat and $150 for house heat (we did a good job sealing up drafts), that ballpark appears accurate. If I optimize a bit, and reduce weekends to 2 swim evenings per weekend than 3 swim evenings per weekend, I can probably cut it further to sub-$300 again including house heat just like I did last year. But we are simming more (12 winter swim evenings a month rather than 8). The bill will arrive within a few days, so I'm quite curious if my prediction is correct.

I may later experiment with a 2h-22h or 3h-21h cycle to see if that uses less weekly natgas, but the coldest month of February might warrant a 5h-19h or 6h-18h timer cycle and/or pool statsis (1h-23h or 2h-22h heat:trickle to maintain pool at 50-60F for 2-3 weeks unused) -- we haven't decided yet if we'll swim at all during -20C forecasts (i.e. below 0F).

I will get some kind of a cheap temperature logger of some sort (SwampWoman, thanks for the tip; I'll opt in for the PC connection option so I can download graphs to Microsoft Excel) -- and get more accurate natgas cost measurements. I'm really starting to hit points of diminishing returns (for a convenient setup) without getting a foam roller cover & adding foam behind the vinyl.

 

[Swampwoman]

^Yes, if I were running like you are that's about right.

In my realm, where I'm running it up to 95 every morning from a typical low of 90, right now I'm averaging more like $14/day or $98 a week...(but when I calculate my useage, I multiply by the efficiency rating for CCF in, so 266 per degree hour is actually 212).

 

[mdrejhon]

Ouch -- I just checked rates -- On January 1st, 2017: My rates rose from 11¢/m³ to around 16¢/m³ before taxes !!! !!!
(rate rise + cap-n-trade started up). So my rates might have just become slightly more expensive than yours.

I may have to revise my bill estimate (to $400-$550 territory including cooking+house furnace -- pool likely being half of this, and house half of this) unless I scale back to 8-day months (2-evening weekends) rather than 12-day months (3-evening weekends). This will likely expedite my procurement of a foam roller cover a little.

P.S. This thread is now 363 days old. This Sunday is this thread's birthday. (I wonder if it belongs in a different topic area of this forum).
_______

EDIT / ADDENDUM: January 20th, mild week, unattended inter-weekend operations
Monday (16th) 12am - end of Sunday swim evening - temperature 93F
Friday (20th) 9am - daily check - temperature 78F
Temperature delta: 15F decrease
Hours elapsed: 105 hours
Heating cycles: 4 periods of 4 hours
Heating hours: 16 hours total over 105 total hours
Comments: Much less debris on pool cover, this weekend will be easier. Current free Cl 3ppm. Rechlorinated twice (+1.5ppm each).
_______

EDIT / ADDEDUM2:
Changed heating cycle to 3h nightly/21h trickle.
Monday (23nd) 1am - end of Sunday swim evening - temperature 94F
TBD
Comments: Weekend is similarly mild as last week, so will be a good fairly scientific comparision to week ending January 20th.

 

[mdrejhon]

New Foam Pool Cover

Been a while, but I have a new upgrade: A foam pool cover.

Basically, 3 millimeter thick laminated foam pool cover.

Cost me 6x the cost of a common bubblewrap pool cover but has a 6 year warranty and hopefully pays off in lower gas costs after just two seasons or so. Initial results are promising.

With raises in gas rates, so optimizing to lower costs even further is important as this is a "luxury" we want to keep doing sometimes.

With evening swims getting chilly again, back to hot tub mode again.
Right now cool temps are arriving (12C nights / 55F, although some 20-25C days / 70-78F). This time the pool is cooling down at only 1C per day from 95F to 90F between the weekends and I only needed 5 hours to reheat to 95F.

I will need to monitor the bills this winter to see how big a difference the foam cover will be. Ground thermometer (4' from pool) is currently reading 70F now. Last winter ground temp four feet away from pool never went below 39F even when air fell below 0F (below -17C).

 

[mdrejhon]

Variable Speed Pump Made a Bigger Than Expected Bill Cut

Also another new observation.

We opted to keep the pool heater route, not the boiler.
-- Raypak Digital 266 is installed.
-- Tristar VS Pump is installed.

After installing the Tristar VS Pump variable speed pump in 2016 to replace that old pig (oink, oink) of a 1.5 kilowatt fixed-speed pool pump.

That one move practically chopped our electricity bill in half; I had never known how much of a oinky pig an old fixed-speed pool pump was. (I actually wonder if that old pump was guzzling more than 1.5 kilowatts).

Here's how much my electricity use went down with the variable speed pump replacing the fixed speed pump.... The house's average power consumption roughly halved!
The investment of almost $1500 on the new pump actually paid for itself in just barely over a year!!!! !!!! !!!!



Bottom is oldest, top is newest data.
The big bars are about $300/mo electricity (before winter 2017) and the small bars are about $150/month electricty (after winter 2017)

We made the move to slow down our pool pump significantly sometime in spring 2017 as the pump is actually larger than our pool really needs. Slowing the pumping speed massively reduced the electricity bill!

It's cheaper to heat using a slower pumping speed on a modern variable-speed pump.

...We experimented with the pool pump programming and tried to figure out if it's cheaper to heat the pool with:
2000 RPM at ~250 watts
2500 RPM at ~400 watts
3000 RPM at ~800 watts
3250 RPM at ~1100 watts

(The numbers varies, I'm going by memory, but it was a logarithmic curve -- higher RPMs required lots more power to speed up further)

We found out that it was actually cheaper to heat the pool a bit slower (most of the time). It made virtually no differnce to the pool heating if I heated at 2000 RPM, 2500 RPM or 3000 RPM -- pumping more slowly simply meant the heater had more time to make the water hotter, so I was still pushing almost the same BTU's into the pool. It's slightly less efficient at slower speed but it made itself up in massive savings ($150 cheaper electricity).
We settled on 2700 RPM(ish) most of the time, but the heater still activates at 2000 RPM pressure.

The pump's electronic display has a built-in wattmeter (like a Kill-a-Watt) so we can monitor how much power the pump uses, it's quite neat to see a pool pump use only 250 watts while still heating the pool as efficiently as a 1.5 kilowatt pump.

Slower moving water simply became hotter to compensate... So pumping speed had virtually negligible impact on heating efficiency (in our situation)
We couldn't tell a difference in heating, but... my scientific knowledge is that it may be slightly less efficiently. Just imperceptibly so. I suspect we might be spending about $20-$30 more natgas to save $150 of electricity by heating the pool little bit more slowly with a variable speed pump. The pool heating efficiency % is almost virtually unchanged regardless of pumping speed. It's slightly reduced by a few percent of efficiency, but the massive electricity savings compensate (and possibly less carbon too, given the grid is not 100% renewable yet).

Pumping at 250 watts instead of 1000 watts still injects practically the same amount of BTUs (we couldn't measure a difference) -- the slower moving water was simply much hotter. Your combined bill (electricity+natgas) thanks you. We preferred stronger jets so we had settled on 2500-2700 RPM as a compromise (the varispeed pump is capable up to 3450 RPM at 1800 watts-ish)

Bottom line, what we've learned is that the ratio of electricity cost to the ratio of gas cost, can be another new weapon in lowering the cost of heating a pool: Don't heat using the maximum pumping speed if your electricity rates are high.

That said, there is a limit how hot you can heat water in the water heater, since water heaters can automatically limit the max water temp of the output (to prevent scalding jets) -- that's when things start becoming inefficient. But in our situation, the jets never become scalding so the safety is never triggered. In a "hotter slow jets" versus "lukewarm fast jets" situation, the pool heats up at the same speed (~1F per hour).


It may be (very slightly) more efficient from the natgas point-of-view to pump faster, but it's a LOT less efficient from the electricity-bill point-of-view. There's a slight efficiency difference, but we couldn't notice. One can view it this way: Instead of wasting more electricity (burning more natgas generators remotely) to pump faster while heating, you might be locally wasting only a few percent more natgas (e.g. burning, say, 3% or 5% more natgas locally) because of slower pump speed, and you still come out ahead financially-wise and carbon-wise. 2000 RPM is still two-third of 3000 RPM, yet it saves roughly 75% of electricity -- and that's where the total-bill economics win.

If your electricity is expensive, pump at 250-500 watts instead of 1100 watts, and spend some of the electricity savings in raising your pool temperature /further/ instead (more hours of heated pump time per dollar) -- and you still come out ahead despite the slightly reduced efficiency -- you're still spending less total bill dollar per BTU injected into the pool (combined natgas+electricity cost).